1. Field of the Invention
The present invention relates to an image forming apparatus, such as an electrophotographic copier, printer, or facsimile, and, in particular, to an image forming apparatus including an intermediate transfer member onto which an image is transferred.
2. Description of the Related Art
Some existing image forming apparatuses include an intermediate transfer belt serving as an intermediate transfer member onto which a toner image formed on a photosensitive drum is transferred. In such image forming apparatuses, in order to control driving of an intermediate transfer belt, a reference mark formed of a light reflecting member is provided on the intermediate transfer belt. In addition, a detection sensor for optically detecting the reference mark is provided.
In order to form an image, such an image forming apparatus performs control so as to start an image forming process after a preset period of time has elapsed since the reference mark was detected by a detection sensor and transfer a toner image onto an intermediate transfer belt at a predetermined position. In addition, when the image forming process is completed, the image forming apparatus performs control so as to stop the intermediate transfer belt after a preset period of time has elapsed since the reference mark was detected by a detection sensor. Thus, the intermediate transfer belt stops at the same position. This is to make a first printout time (hereinafter also referred to as an “FPOT”) constant.
Since the intermediate transfer belt is held tight around a plurality of support rollers, partial wrinkle of the intermediate transfer belt may occur at a position at which the intermediate transfer belt is in contact with the support roller if, as described above, the intermediate transfer belt stops at the same position. If a wrinkle occurs, a toner image transferred onto the intermediate transfer member cannot be transferred onto a recording material at an accurate position. Accordingly, an image defect, such as white streaking, may occur. To address such an issue, Japanese Patent Laid-Open No. 2001-201994 describes a technique for reducing the probability of the occurrence of such an image defect caused by a wrinkle of an intermediate transfer belt by performing control so that the intermediate transfer belt stops at least two different positions.
If, as described in Japanese Patent Laid-Open No. 2001-201994, the intermediate transfer belt is stopped at least two different positions, the occurrence of an image defect caused by a wrinkle can be reduced. However, if a difference between the length of the intermediate transfer member and the length of a transferred toner image is small, the toner image is forced to be transferred onto a wrinkle of the intermediate transfer member and, therefore, an image defect occurs in the toner image transferred onto the wrinkle.